This is the real issue in these situations. There really isn't a good place to pee in a lot of places. People often as not rely on restrooms provided by businesses and they only let you go in there if you are a customer. So if you're not... or they're closed because it is late... then where are you going to pee?
The issue with public restrooms is that that is realestate that is valudable and you have to police and maintain them to keep people from selling drugs for blow jobs in them or rubbing shit into the ceiling.
The Solution there is to have them be public but make their maintenance the responsibility of locals rather than some city workers that will be under staffed, unmotivated, and unaccountable when they don't do their jobs. Local businesses will want those facilities to look good and be good and so they'll task someone to deal with it.
Regardless, anyone that thinks they're stopping people from peeing by putting funny paint on the walls is an idiot.
1. You can still pee on the ground.
2. Stand back and pee at an angle and you can pee on the wall.
3. Women are responsible for this far more than you'd realize and they pop a squat and pee.
So... yeah. You're not stopping anything with your paint. Put in more public bathrooms or get used to the smell of urine.
Maintenance doesn't have to be a problem for public bathrooms. Unless it is in a remote area, a 1st-world public bathroom requires water and sewer connections. Make the whole thing out of plastics / stainless / tile and put in sloping floors and a floor drain. Put some retractable rotating water jets in the ceiling, and have them go off at 3AM every day and with an occupancy sensor. I'm thinking like a soot blower (PDF) kind of device, but with water. To reduce complexity you could power the rotation with a small water turbine or just make the nozzles with 360 degree coverage. Most cities have very impressive water pressure in the early AM hours, so a pump shouldn't be required.
Japanese public bathrooms sometimes don't have toilet paper or paper hand towels. People are in the habit of carrying their own. It is better to have a bathroom and bring your own paper than to have no bathrooms at all.
A bathroom built like this wouldn't need regular cleaning or restocking. You could put them on the sidewalk in high-traffic areas to avoid having to purchase land. It's a public good, and exactly the sort of thing governments should provide.